The performance of such testing has improved thanks to the increase of the work load, use of computerized analysis, and use of multivariate discriminant analysis.
Nevertheless, the problem of interpreting the significance of the ST-segment depression with upsloping morphology has remained unsolved. It is accepted that the upsloping morphology represents a transition between the physiological depression of the J-point and the "ischemic" morphologies, represented by 1 or more mm of horizontal or downsloping depression, measured at 80 msec after the J-point.
Different criteria has been proposed to cope with different-combinations of the depression and slope, but none was described by a closed mathematical expression, derived exclusively from theoretical properties of the ST-segment.
Three basic problems with the ST-segment analysis had to be solved:
(1 ) lack of a criterion to express the equivalence between different morphologies. PA0 (2) need to explain the unreliable behavior of the ST-segment integral (area) (Sheffield's index). PA0 (3) need to create a theoretical background for the ST-segment analysis.